Software upgrades typically require that a system is taken out of service for a time period. During the software upgrade, systems are isolated from the network inputs and do not provide system functionality to the deployed topology. After the software upgrade, the system is gradually introduced to the network via a test phase, after which actual inputs may be introduced. A typical requirement from a service provider for a software upgrade in a network is that the upgrade should be restricted to a maintenance window (MW) of about 4 hours. This maintenance window is generally during non-peak hours, such as 2 AM to 6 AM. The idea is that there is minimal network activity during non-peak hours. With less traffic, and network elements can be upgraded in a relatively quiescent period without adversely affecting the operations of the network.
In next generation networks (e.g., 4th Generation networks), data traffic rarely goes down to zero or near-zero during the non-peak hours. Users install and run applications on their smart devices that continually ping the network and get updates. Therefore, if a system is completely removed from service for a software upgrade, there may be an undesirable interruption of operations within the network. Service providers continually look for ways to perform software upgrades that are less disruptive to network operations, require minimal operator involvement, and consume the least amount of time.